Grid alignment in electron tubes



Feb. 19, 1957 w. J. RHYNE GRID ALIGNMENT IN ELECTRON TUBES Filed D6 1953D8 0 aouo v? Mum Feb. 19, 1957 I w. J. RHYNE 2,782,338

GRID ALIGNMENT IN ELECTRON TUBES Filed Dec. 9, 1953 GRID ALIGNMENT INELECTRON TUBES William LRhyne, Prospect Park, Pa., assignor to SylvaniaElectric Products Inc., a corporation of Massachusetts ApplicationDecember 9, 1953, Serial No. 397,131

4 Claims. (Cl. 313-299) This invention relates to means and methods-formounting and aligning the grid elements of an electron discharge deviceand more particularly to meansand methods for mounting and aligning thegrid elements of a beam. type electron discharge device.

In a conventional beam type tube such as the '6L6G, the electrode mountis assembled by threading the upper and lower extremities of supportelements for the electrodes through upper and lower insulating spacers,said spacers having apertures therein for positioning and retaining thesupport elements, and therefore the electrodes with respect to eachother. Upon completion of this mount assembly, weld connections are madebetween grid side-rods and their corresponding stern leads. Lateralwires of the grid are then visually aligned with one another. Since thisassembly operation includes mounting and welding the anode in its finalposition, visual observation necessary for alignment of the grids isobstructed by the anode.

Heretofore, several procedures and means have been devised to accomplishand maintain correct grid alignment until the construction andprocessing of the tube has been completed. In each procedure theconfiguration of the anode was made so as to facilitate observation ofat least several turns of the grid lateral wires by the mountingoperator. One method utilizes an observation window cut into the centralregion of the anode. Another method relies on an anode which has asmaller axial length then the axial length of the grid lateral wirecoverage so that several lateral wire turns can be observed either aboveor below the edges of the anode. Still another method uses anode halfplates so that alignment of the grids can be made after one of the anodehalf plates has been mounted, and before the opposing half plate iswelded in position.

These procedures have the disadvantages of not providing for sufficientgrid coverage by the anode, or requiring additional steps in thefabrication of the anode,

or of limiting grid lateral wire area available for'observation duringthe alignment operation.

One object of this invention is to obviate the aforesaid difiiculties inthe manufacture of a beam type electron discharge device.

Another object is to provide in a device of the aforesaid character, abetter grid alignment, thereby providing for a more efficient beam typedevice.

A further object is to provide for improved means for firmly andaccurately positioning the electrodes of an electron discharge devicewith respect to each other within the envelope.

A still further object is to provide for improved means for restrictingthe vibrational movement of the electrodes of an electron dischargedevice under operating conditions A still further object is to providefor an electron discharge device with a very low microphoniccharacteristic.

A still further object is to-provide an improved method nited StatesPatent 'ice for constructing a beam type electron discharge device, andmore particularly for an improved method of mounting and laterallyaligning the grids of a beam type electron discharge device.

A beam type electron discharge device according to the present inventionrelates to a tube comprising a cathode, an anode, beam confining plates,and a plurality of nested grids. These grids are all wound with the samenumber of lateral wire turns per inch so that each lateral wire turn ofone grid shades the corresponding lateral wire turn of another grid fromthe cathode. The beam confining plates substantially limit the flow ofelectrons to the area. of the anode which faces the minor axis of thegrids.

For a better understanding of the invention, reference is made to thefollowing description taken in connection with the accompanying drawingsin which:

Fig. 1 is a partially sectionalized perspective view of an electrondischarge device made in accordance with my invention.

Fig. 2 is an exploded view of an electron discharge device mountembodying the elements constituting my invention.

Fig. 3 is a view of the front of two grids which are not laterallyaligned.

Fig. 4 is a similar view of the same two grids after they have beenproperly laterally aligned.

Fig. 5 is a plan view of an electrode mount made in accordance with myinvention showing a top spacer parti ally cut away to expose a lowerspacer.

The electron discharge device shown in Fig. 1 has a conventional vacuumtight enclosure or envelope 1t) and external circuit connecting pins 12.Mounted within the envelope are the conventional elements of amulti-grid tube, supported and positioned by the insulating spacers 14and 16.

' In accordance with my invention the cathode 18, control grid 20,screen grid 22, and beam confining plates 24 are supported and correctlypositioned withrespect to .each other at their lower extremities by aninsulating spacer l4, and at their upper extremities by an aligninginsulating spacer .26 in addition to the insulating spacer 16. Thealigning spacer 26 is mounted between the lower surface of the spacer 16and the upper lateral wire turns of the grids 20 and 22. In thisconstruction it can be seen that spacer 26 is Within the confines ofanode 28. The anode 28 is supported at its lower extremity by the spacer14 and at its upper extremity solely by the spacer l6.

The method of mounting the electrode of the electron discharge deviceembodied in my invention is best shown in Fig. 2. The cathode 18 isfirst threaded through the central aperture of spacer 14. The controlgrid 20 and screen grid 22 are then dropped over the cathode 18 and theside-rods of these grids are threaded through corresponding apertures inspacer 14. The beam confining plates 24 are subsequently positioned bythreading their mounting appendages 30 through the correspondingapertures inspacer 14. The aligning spacer 26 is then slipped over theelectrodes by orientating and associating the apertures in the aligningspacer 26 with the cathode 1S, side-rods of the grids 2t) and 22, andmounting elongated appendages 31 of the beam confining plates 24. Whenthis sub-assembly i completed, the side-rods of the grids 20 and 22 arewelded attheir lower extremities to the leads 34 protruding from thestern.

Fig. 3 indicates the axial displacement of the leteral wires of thecontrol grid 20 with relation to the lateral wires of the screen grid 22which may occur after the aforementioned Welding operation has beencompleted. The grids 2t 22 are at this time supported against verticalmovement at their lower extremities by the weld connections to the sternleads 34 and transversely supported at their lower and upper extremitiesby spacers 14 and 26. The next step in the process is to laterally alignthe grids. This is effected by bending such stem leads 34 as isrequisite to raise and lower the grids 20 and 22 to effect thealignment. Fig. 4 shows such alignment of grids. These grids will retainthis position through subsequent operations and processing of the tube.

To complete the assembly, the anode 28 is slipped over the anode supportrods 32 and the spacer 16 is placed in position by orientating andassociating the mounting support elements of the cathode 18, grids 20and 22, beam confining plates 24, and anode 28 with the con respondingapertures in spacer 16. The necessary remaining welds and electricalconnections are then made to complete the electron discharge devicemount assembly. It is possible to so position the anode on the rods 32because of the spacer 26 being of a size to fit within the confines ofanode 28 as shown in Figures 2 and 5.

Another notable feature present in an electron discharge device made inacordance with my invention means, namely spacers 16 and 26, provided atthe upper extremities of the support rods for the cathode 18, grids 20and 22, and beam confining plates 24. Since the upper part of theelectrode mount is normally less secure than the lower part, this doubleretention means is very efficient. It is generally accepted in the tubemaking industry that vibrational movement of the grids and beamconfining plates under tube operating conditions are the chief causes ofmicrophonism. Since the spacer 26 is positioned very close to the toplateral turns of the grids 20 and 22 and abuts the upper edges of thebeam confining plates 24, these elements are held in an unusually secureposition. This holding of parts securely in position is enhanced byspacing the element 26 away from the spacer 16, thereby securing threelevel supports for the tube elements.

Another advantage of the method of mounting the electrodes for anelectron discharge device is the simplified manner in which thi mountingoperation is achieved. My method provides for an increase inmanufacturing efiiciency due to the decrease in grid losses over thoseoccurring in normal mounting operations, and to a decrease in the amountof tubes rejected for high screen current in a beam type tube. Theselosses are caused by a displacement of one or more of the grid lateralwires resulting from the anode being bumped against one or more of thegrids during the anode dropping operation. Heretofore the cathode 18 andgrids 20 and 22 were threaded into the apertures in spacer 14 and thenthe anode 28 was dropped over these and into position. Since the gridsare retained only by the spacer 14 during the anode mounting operation,they often assume a position which is not perpendicular to the planarsurface of the spacer and therefore cause difliculty in getting theanode over the grids without bumping them. The majority of the losseshas been caused by displacement of the first few top turns of the grid22.

Utilizing the electrode mounting method of the invention avoidsafore-mentioned difiiculties since the spacer 26 is mounted prior to theanode dropping operation, thus supporting and positioning the gridsbefore the operation. An important feature of this method is thephysical protection of the grid lateral wires against damage by thespacer 26 While the anode is being placed in position. The importance ofthis novel process will be more fully appreciated with a realization ofthe small distances between the elements with which the mountingoperator must contend.

I have found that the methods employed by me in the construction ofelectron discharge devices produces a more efficient tube with acorrespondingly greater power output and lower screen current thanheretofore, since it provides for visual observation of the entire axiallength of the grids during the alignment operation and from both sidesof the mount; furthermore, my method insures this alignment to remainintact during subsequent assembly and processing operations. Inaddition, I have found that the unique double retention means providedat the upper extremities of the mount electrodes greatly decreasesvibrational movement of these electrodes, resulting in the production ofan electron discharge device with an improved microphoniccharacteristic.

Obviously, the mount electrodes, according to the present invention, mayhave different configurations. In addition, the lateral alignment of thenested grid electrode wires is not intended to be restricted to themanner of aligning the grids as described in a beam type electrondischarge device and shown by Fig. 4 of the accompanying drawing. It isobvious that a lateral grid wire alignment may be desirable wherein thelateral Wires of a grid do not shade the lateral wires of the remaininggrids from the cathode. In either event the utilization of the spacer 26permits facile proper positioning of the grid laterals with respect toone and other.

While I have indicated a single embodiment of my invention, it will beapparent to one skilled in the art that variations may be made in thedescribed structure and process without departing from the scope of myinvention as set forth in the appended claims.

. What I claim as new is:

1. In an electron discharge device including nested grids with thelateral wires of one grid aligned with the lateral wires of anothergrid, and an anode, each of said grids and anode having elongatedsupport elements thereon, the combination comprising a first insulatingspacer receiving and positioning the one ends of said support elements,a second insulating spacer within the confines of the anode receivingand positioning the opposite ends of the grid support elements, and athird insulating spacer receiving and positioning the opposite ends ofboth the anode support elements and at least one of the support elementsfor each grid.

2. In an electron discharge device including nested grids with thelateral wires of one grid aligned with the lateral wires of anothergrid, beam confining plates, and an anode, each having elongated supportelements thereon, the combination comprising a first insulating spacerreceiving and positioning the one ends of said support elements, asecond insulating spacer within the confines of the anode receiving andpositioning the opposite ends of the grid and beam confining platesupport elements, and a third insulating spacer receiving andpositioning the opposite ends of all of said support elements.

3. In the process of assemblying an electrode mount for an electrondischarge device, the steps of mounting the one ends of elongatedsupport elements forming part of nested grids on a first insulatingspacer, mounting a second insulating spacer on the opposite ends of thesupport elements of the grids, laterally aligning the lateral wires ofthe grids with respect to each other, mounting the one end of elongatedsupport elements forming part of an anode on said first spacer, andsubsequently mounting a third insulating spacer on the opposite ends ofthe support elements of said anode and on the opposite end of at leastone support element of each grid.

4. In the process of assemblying an electrode mount for an electrondischarge device, the steps of mounting the one ends of elongatedsupport elements forming part of nested grids and beam confining plateson a first insulating spacer, mounting a second insulating spacer on theopposite ends of the support elements of the grids and beam confiningplates, laterally aligning the lateral wires of the grids with respectto each other, mounting one end of elongated support elements formingpart of References Cited in the file of this patent UNITED STATESPATENTS 2,042,057 Hopping May 26, 1936 6 Schade Feb. 8, 1938 Parker Dec.12, 1939 Peterson Oct. 8, 1940 Ronci June 1, 1948

